The present invention relates to tracking ocean submerged cables and more particularly to a sensor for generating guidance signals to control the direction of the tracker.
An unmanned device for automatically tracking and burying existing seafloor communication cables requires a tracking/guidance system to follow the cable as it lies on the ocean floor.
There are several known systems for tracking, such as the sensors of U.S. Pat. Nos. 3,213,360; 3,323,699; 3,702,957; 4,317,079 and 4,338,043. The sensors of U.S. Pat. Nos. 3,213,360; 3,323,699 and 3,702,957 require that all conductive elements, including those in the item being tracked, to be connected into the sensor circuit by hard wire or through ground contacts. If an electrical cable is being tracked, connections to the conductive elements require destruction of the electrical insulation at many locations as the system moves along the cables.
The sensor of U.S. Pat. No. 4,317,079 requires an electric generator be hard wired to the conductors of the cable being tracked. Due to electrical losses in a long cable, the generator must be moved and reconnected to the cable conductors as the cable is tracked, resulting in the destruction of the electrical insulation.
The sensor of U.S. Pat. No. 4,338,043 projects ultrasonic energy toward the object being located and detects the energy reflected back from that object. This system cannot detect an object shielded from the projected ultrasonic energy by the ocean floor or a small object that has an acoustic impedance similar to its environment.